Hypertensive crisis refers to the complication of primary and secondary hypertension in which, under the influence of certain predisposing factors, the peripheral arterioles undergo temporary and intense spasms during the course of disease development, leading to a sharp increase in blood pressure, a sharp deterioration of the condition, and severe damage to the functions of major target organs such as the heart, brain, and kidneys caused by hypertension. In addition, if the diastolic blood pressure is higher than 18.3-19.6 kPa (140-150 mmHg) and/or the systolic blood pressure is lower than 28.8 kPa (220 mmHg), it should be regarded as a hypertensive crisis regardless of the presence or absence of symptoms.